It is often desirable to treat large numbers of individuals or animals with a substance, such as a medication or other material, with speed, efficiency, accuracy, and accurate maintenance of records. As an example, the livestock industry requires routine vaccinating, medicating and/or treating of cattle or livestock. Failure to properly treat the animals can result in significant losses to the rancher or feedlot owner or other party responsible for the livestock. Typically, the livestock is segregated into groups according to general size and weight. It is common upon arrival at the processing station for cattle to be vaccinated for viral respiratory disease implanted with a growth stimulant, and treated for internal and external parasites. In high stress situations, antibiotics are sometimes administered simultaneously with vaccinations.
To assist in vaccination large numbers of animals, portable syringe injections systems have been developed that allow a syringe to be filled by a pump from a fill bottle, where the dose loaded into the syringe can be effectively controlled and varied as needed to tailor the injections by animal weight. Such a syringe system does not require the cumbersome filling of the syringe from a separate fluid container, allows for repeated injections, using precisely predetermined but differing dosages, and are capable of operating in a wide range of environments. One such syringe system is shown in U.S. Pat. No. 7,056,307, hereby incorporated by reference As shown in FIG. 1, a syringe system will include a fill or reservoir bottle 2, a syringe 10, a highly accurate reversible pump 4 and associated motor or drive 5, and various fluid lines between the components. The preferred system unit pump 4 is a valveless, substantially viscosity-independent pump. The pump 4 used in the preferred system is manufactured by Fluid Metering, Inc. (“FMI”) of Syosset, N.Y., Models STH and STQ. To the extent necessary to understand the features and construction of the pump 4 manufactured by FMI, Applicant hereby incorporates by reference U.S. Pat. Nos. 5,279,210; 5,246,354; 5,044,889; 5,020,980; 5,015,157; and 4,941,809. A complete FMI pump cycle includes a ½ cycle of gathering fluids from the reservoir lines, and a second ½ cycle of pumping the gathered fluid out the fluid line 6 (that is, the pump is not continuously pumping fluids as would, for instance, and impeller type pump).
As used herein, the system pump 4 will be considered as a fluid pressurizing means. The pump 4 can supply positive pressures to the syringe 10 when activated to pump fluid from the reservoir bottle 2 to the syringe 10, or negative pressures (suction) when pumping fluid from the syringe 10 to the reservoir bottle 2. For purposes of this application, when the pump 4 is not active, the pump is considered as providing no applied pressure (e.g. 0 pressure) to the syringe. For purposes of this application, a dual cycle pump like the FMI pump, as long as the pump 4 is active in a forward or reverse pumping mode, is considered as supplying pressures for the entire cycle, even though for ½ cycle the pump 4 does not deliver fluid to the syringe. There are implications of this ½ cycle to the invention that will be addressed later.
To control fluid movements in the syringe, valves are used. Prior art syringes utilized check valves or spool valves. For check valves, a first check valve is located between the syringe barrel and the discharge port and is connected such that fluid flow is possible only from the syringe cylinder to the discharge port, but not a counter flow such as might occur when drawing fluid from the fluid container connected with the syringe. A second check valve allows a fluid flow from the fluid container through a supply port in the syringe to the syringe barrel when pulling back the plunger, but not when advancing the plunger. A more compact valve system is the use of a single spool valve whose relative movement alternatively blocks the supply port or discharge port, or in an intermediate position, blocks both ports. One such spool valve is shown in U.S. Pat. No. 6,989,000 (hereby incorporated by reference) and uses a flexible membrane as the movable valve member. The single check valve is more efficient, has fewer parts and allows for more readily assembly of a completed syringe.
Unfortunately, the spool valve functions as a one way valve, and hence, it is not possible to empty the syringe of fluids by reversing the fluid pump. Further, due to the many sub-components of the spool valve assembly, cleaning of the syringe usually requires complete disassembly of the complicated valve assembly, a time consuming task. To remove spool valve from the valve chamber (the void inside the metal valve housing), the valve housing must be unscrewed from the syringe head, thereby leaking medicine out of the chamber. After reassembly, fluid and air in the supply line must be purged from the line and spool valve assembly. Enabling the fluid pump will open the spool valve, opening the fluid path into the syringe barrel for purging. But squeezing the syringe handle, to purge the air from the syringe barrel out through the discharge port, sometimes causes a lockup condition. This is due to compressible air trapped on top of and in the spool valve chamber space, and the incompressible fluid below the valve, which fails to open the spool valve nose seated at the discharge port. Also, air can be trapped within the space between the flexible diaphragm and the upper plastic parts, since these are not in the immediate fluid path but are only intended to be a pressure chamber off of the main fluid path.
Additionally, the spring tension on the spool valve is set with an adjustment set screw which is inside the valve housing assembly, a poor location. If the spring tension is set for low fluid pressure at low filling speeds, the plunger fails to seat when the fluid is changed to a high fluid pressure due to high pump speed and vice versa. Hence, pressure adjustments require disassembly of part of the syringe in order to adjust spring tension, and de to lack of references for set screw position (as the spool valve may be rotating in the valve chamber with the screw) the actual degree of tension is thus set by trial an error.
Other problems associated with the spool valve include: (a) with the spool valve resting in the intermediate position (sealing both the input or supply fill port and the discharge port), extra manual pressure must be made at the syringe handle to overcome the pressure necessary to compress the spool valve spring to open the discharge port if the spool valve has been adjusted for high speed and pressure fluid filling; (b) when the spool valve is extended in the intermediate position, the spool valve will remain on the midline between the input and the discharge ports, but when fluid pressure is supplied, the terminal end of the valve may pivot off the center line and fail to realign with the open port when pressure is released, causing it to hang up on the sides of the valve chamber due to fluid viscosity, causing a lockup condition; (c) with the spool valve in the intermediate position, the syringe will not function as a manual fill syringe by means of allowing a user to pull the syringe handle back, loading fluid back in through the syringe needle into the syringe barrel. While a single valve mechanism is preferred, a valve without the limitations of the spool valve is needed.